Smooth-bore nozzles are in common use on the fire ground for extinguishing and controlling fires using water, foam, compressed air foam, or dry chemicals. It is common to have a series of two or more nozzles assembled into a stack with the smallest nozzle on the end of the stack, and progressively larger nozzles underneath. Normally the nozzles are connected to each other with fire hose threads or a quick connecting coupling such as a Storz coupling.
Between fires, the nozzles remain connected in series to prevent the disconnected elements from being lost or misplaced at the scene of a fire. Consequently, the smallest nozzle by default is the one ready for deployment at the start of a fire. Unfortunately, the smallest nozzle provides the least protective fire knockdown power and compromises the effectiveness of the firefighter. Moreover, when the flow of the smaller nozzle proves insufficient, then precious time must be spent to shut down the flow, remove the smaller nozzle, and find a pocket or other convenient location to keep the smaller nozzle in case it is needed again.
Firefighting nozzles with multiple-sized orifices arranged with their central axes parallel to the axis of the hose line have been devised. Some prior art nozzles had a series of orifices arranged to be brought into alignment in the manner of a cylinder on a six-shooter revolver, or worked by diverting the discharge in the manner of a double barrel shotgun (under/over, or side-by side). Other multiple-orifice nozzles have been described as having a rotating head and several nozzles. In these prior art devices, the orifice type and size must be engineered into the product, leaving the user without any opportunity to connect a discharge tip of his or her own choosing.
Still other nozzle designs have diverted some or all of the flow through a secondary channel to give concentric discharge of an outer spray pattern and an inner spray pattern. When both nozzles are operated in series, these devices do not have a simple smooth-bore shape with an unobstructed flow. As such, they do not appeal to firefighters who believe that the simple, unobstructed, tapered cylindrical waterway of a smooth-bore nozzle is the most effective. While peripheral jet nozzles have sought to overcome this drawback by means of an orifice whose size is adjustable, the abrupt changes in direction or flow area of this nozzle type is well known to degrade the quality of compressed air foam. Thus, their use with compressed air foam systems (CAFS) is generally frowned upon.
A variant on smooth-bore nozzles for use with CAFS was patented by Elkhart Brass as a “adjustable smooth bore nozzle.” That arrangement has a membrane whose at-rest diameter is smaller than the maximum diameter desired as indicated by the diameter adjustment setting on the nozzle. When operating at the maximum condition, the membrane must be expanded to a larger size, and this expansion exerts pressure on the foam and thus constricts the foam and degrades the properties of the foam.
Both the peripheral-jet and the adjustable, smooth-bore nozzle types have internal mechanisms that use an external control system to change the internal size of movable members. The position of the external control device must be interpreted by markings to determine what setting the nozzle is in. Some firemen prefer the simplicity of observing a simple round discharge opening for discharging fluids at a fire. Those arrangements are easy to understand, and it is visually obvious which size nozzle has been brought to bear on the fire without having to interpret markings, which can be difficult in situations where visibility may be obscured by smoke or darkness.